In recent years, the use of light-emitting diodes (LEDs) for various common lighting purposes has increased, and this trend has accelerated as advances have been made in LEDs and in LED-array bearing devices, often referred to as “LED modules.” Indeed, lighting applications which have been served by fixtures using high-intensity discharge (HID) lamps and other light sources are now increasingly being to be served by LED modules. Such lighting applications include, among a good many others, roadway lighting, parking lot lighting and factory lighting. Creative work continues on development of lighting fixtures utilizing LED modules. It is the latter field to which this invention relates.
High-luminance light fixtures using LED modules as light source present particularly challenging problems. High costs due to high complexity becomes a particularly difficult problem when high luminance, reliability, and durability are essential to product success. Keeping LEDs and LED-supporting electronics in a water/air-tight environment may also be problematic, particularly when, as with roadway lights and the like, the light fixtures are constantly exposed to the elements. Use of a plurality of LED modules presents further challenges.
Yet another cost-related challenge is the problem of achieving a high level of adaptability in order to meet a wide variety of different luminance requirements. In other words, providing a fixture which can be adapted to give significantly greater or lesser amounts of luminance as deemed appropriate for particular applications is a difficult problem. Light-fixture adaptability is an important goal for LED light fixtures.
The product safety of lighting fixtures creates an additional area of difficulty, and such fixtures are most often required to comply with standards put forward by organizations such as Underwriters Laboratories Inc. (UL) in order to gain acceptance in the marketplace. One such set of standards deals with the accessibility of the electrically-active parts of a fixture during operation, and, more importantly, during periods of stress on the fixture such as in a fire situation during which some elements of the lighting fixture are compromised. The UL “finger test” mandates that a human finger of certain “standard” dimensions (defined in NMX-J-324-ANCE, UL1598, Dec. 30, 2004, Figure 19.22.1, page 231) should not be able come in contact with any electrically-live parts of the fixture under such circumstances. The standards also establish certain material limitations on the enclosures of such products, all of which are dependent on the voltages and power levels within the fixtures.
Increased product safety can be costly to achieve and reduced optical efficiency in many cases may be a result of improving product safety. For example, placing a fixture behind a sheet of glass to provide increased safety can result in an optical efficiency loss of up to 10%.
For LED-based lighting fixtures, the cost of the power supply is an important part of the overall fixture cost. When a large number of LEDs are used to provide the necessary level of illumination, it is advantageous to use a single power supply providing higher voltages and higher power levels, which, in turn, requires more stringent safety standards. In particular, power supplies with a Class 2 power supply rating are limited to 100 watts at a maximum of 60 volts (30 volts if under wet conditions). LED-based lighting fixtures with a large number of LEDs can benefit (both by cost and efficiency) by using a Class 1 power supply, in which both the power and voltage limitations of a Class 2 power supply are exceeded. If power requirements for a lighting fixture are higher than the Class 2 limits, then multiple Class 2 power supplies are required (which can be costly) unless the more stringent safety standards which using a Class 1 supply brings about can be achieved.
As mentioned above, such more stringent requirements include satisfying the “finger test” under certain fire conditions during which it is possible that lighting module elements such as lenses made of polymeric materials may be removed. For example, in an LED device with a primary lens made of glass and a secondary lens made of polymeric material, it is necessary to provide enclosure barriers over the entire electrical portion of the module (on which the LED devices are mounted) except over the primary lenses. It is assumed that under these circumstances, the polymeric secondary lenses will be destroyed in the fire, leaving the primary lenses exposed. Also for example, if a single polymeric lens is used in place of both the primary and secondary lenses, then the enclosure barriers must prevent “standard finger” access to the electrical elements in situations in which the single lens is no longer in place.
Thus there is a need for improved LED lighting fixtures which can better serve the requirements of general-illumination lighting fixtures and which can provide both the safety and cost-effectiveness which the marketplace requires and/or prefers.
In short, there is a significant need in the lighting industry for an improvement in manufacturing lighting fixtures using LEDs, addressing the problems and concerns referred to above.